Laser beam reference line means and method

ABSTRACT

The invention comprises means and a method for establishing a reference line for construction purposes in the form of a energy beam or signal, such as a visible light beam, and preferably, a laser beam. The apparatus includes an energy beam source, adjustably mounted within a housing, pendulously suspended for movement within a vertical plane. The energy beam source and housing are stabilized with respect to a suspension point, so that the energy beam source and housing assume a stable, horizontal position. The apparatus further includes tridimensional adjustment mechanisms for the energy beam source and a stable support for the suspension point. The method of the invention includes the steps of establishing a line offset 90* to the reference line, placing the energy beam source approximately coincident to the reference line, adjusting the energy beam source vertically to coincide with the depth of the reference line, adjusting the energy beam source internally of its housing to desired grade, adjusting the energy beam source to coincide with the reference line in a horizontal plane, and interrupting the projection of the energy beam source to check true vertical plane alignment.

United States Patent 1 3,612,700

[72] inventor Rodney L. Nelson Primary Examiner-Ronald L. Wibert Box N, RD. #1, Falls Creek, Pa. 15840 Assistant Examiner.l. Rothenberg [2i 1 Appl. No. 792,290 Attorneys-Keith Misegades and George R. Douglas, Jr.

[22] Filed Jan.21,l969 [45] Patented Oct. 12,1971

ABSTRACT: The invention comprises means and a method for establishing a reference line for construction purposes in the form of a energy beam or signal, such as a visible light beam, and preferably, a laser beam. The apparatus includes an energy beam source, adjustably mounted within a housing,

pendulously suspended for movement within a vertical plane.

[ LASER BEAM REFERENCE LINE MEANS AND The energy beam source and housing are stabilized with METHOD respect to a suspension point, so that the energy beam source and housing assume a stable, horizontal position. The ap- 18 Claims 15 Drawing Flgs' paratus further includes tridimensional adjustment [52] (L5. Cl 356/153, mechanisms for the energy beam ource and a table support /4 33/73 D, 240/78 for the suspension point. The method of the invention includes [5 Int. the te s of establishing a line offset 90 to the reference line G013 l5/00 placing the energy beam source approximately coincident to Field Of Search the reference line adjusting the energy beam source vertically 46, 73 D, 70 to coincide with the depth of the reference line, adjusting the 240/78, 85, energy beam source internally of its housing to desired grade,

adjusting the energy beam source to coincide with the [56] References cued reference line in a horizontal plane, and interrupting the pro- UNITED STATES PATENTS jection of the energy beam source to check true vertical plane 3,279,070 10/1966 Blount et al. 33/74 X alignment.

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a Q ODNEY L. NELSON 98 '00 FlG. lO BY ATTORNEY PATENTEDncT 12 l97l 3, 12,700

sum u (If 5 INVENTOR RODNEY L. NELSON ATTORNEY PATENTEDum 12 l97| SHEET 5 0F 5 FIG.|4

INVENTOR (nmiODNEY L. NELfiN ATTORNEY LASER BEAM REFERENCE LINE MEANS AND METHOD BACKGROUND OF THE INVENTION The invention relates generally to method and means for establishing a reference line for construction purposes, and more particularly, for determining a reference line useful in the laying of subterranean pipeline, such as sewer pipe.

In the normal course of events, the laying of sewer pipeline necessarily involves undue computation and considerable double checking of grade and alignment of the pipeline as it is laid in place. The usual method involves the well-known batterboard and chalkline system, which comprises surveying the course of a sewer pipeline, marking ofi manhole location at distances of approximately 400 feet or so between manholes, and setting up batterboards at distances of 20 or 25 feet from each other between manholes. First, the batterboards are set to proper grade by a team of surveyors employing a transit and a level. Then a chalkline is strung across the batterboards as an offset line of reference for the eventual pipeline. As the pipeline is laid, a gauge pole is suspended from the chalkline to the individual pipe unit, vertical alignment being established by use of a plumb bob. Of necessity, the usual gauge pole if from to feet long, sufficient to traverse the vertical offset distance between the chalkline ofi'set and the pipeline. lnherently, the batterboard system presents far too many possibilities for error. Additionally, too many men must be employed in the operation. Of course, the largest expense involved is the cost of the transit and level crew, which must be constantly on the job to set new batterboards as the pipe laying process proceeds.

U.S. Pat. No. 3,136,062 issued to James C. Garwood illustrates a slight improvement in the pipe laying process, but the system proposed still involves the use of batterboards. Incidentally, a full explanation of the batterboard system of pipeline laying appears therein. Another improved method of pipeline laying is disclosed by US. Pat. No. 3,314,068 issued to Alphonse Verive, which, in its principal embodiment, discloses a radio or radar signal system, offset from the pipeline, for establishing line and grade of each pipe segment being laid. However, employment of that method involves the cost and expenses of sophisticated, knowledgeable employees.

An improvement in the pipeline methods thus expenses discussed is illustrated by US. Pat. No. 3,l 16,557 issued to James R. Trice, IL, and U.S. Pat. No. 3,279,070 issued to Glen R. Blount. Both of these patents illustrate the use of a light beam reference line, which is established coincident with the desired line and grade for the actual pipeline. However,

the system disclosed by the former patent requires the employment of a transit and numerous incremental micrometer adjustments to establish the beam upon true line and grade, as set forth in column 4 of the patent specification. The latter patent also requires the use of a sighting device 11 which is mechanically slaved to the light beam source housing in order to establish the beam on line and grade.

On the other hand, the instant invention requires no additional sophisticated equipment for establishing the light reference beam on true line and grade beyond the establishment of a 90 ofi'set line set to a known grade. Once the offset line is established, relatively unskilled workmen may easily set the energy beam source to true line and grade. Obviously, the first immediate advantage of the invention is the elimination of costly labor in establishing the appropriate reference line. Secondly, substantial cost savings are provided in that the invention is of optimum simplicity. Thirdly, the energy beam source is contained within a housing, counterbalanced and pendulously suspended so as to be freely movable within a vertical plane, the energy beam source itself being adjustable within a vertical plane interiorally of the housing itself. In this manner, the appropriate grade for the reference line may be established elsewhere than on the job location.

SUMMARY OF THE INVENTION The gist of the invention is to provide an apparatus for establishing a reference line for construction purposes comprising an energy beam or light beam which is set directly coincident with the true reference line. The apparatus of the invention includes an energy beam source, contained within a support housing, which is counterbalanced with respect to a pendulous suspension point. The energy beam source is freely adjustable within the housing, within a vertical plane, and includes means-indicating deviation of the energy beam source from a true horizontal plane. Additionally, means are provided to adjust the energy beam source housing, incrementally, about a vertical axis. A prism assembly is provided to interrupt the energy beam and direct it to a system for checking alignment of the energy beam source in a vertical plane. The energy beam source is preferably in the form of a laser beam, and may be arranged to direct a beam forwardly as well as rearwardly of the support housing. The-method of the invention comprises establishing an offset line at a known grade, adjusting the energy beam source vertically to coincide with the desired depth of the reference line, adjusting the energy beam source to desired grade within its support tube, supporting a horizontal reference line vertically adjacent the energy beam source, interrupting the impulse source and projecting the beam to the horizontal reference line for true vertical plane alignment of the source, and adjusting the source about a vertical axis, if necessary, so that the energy beam is directed within the desired vertical plane.

BRIEF DESCRIPTION OF THE DRAWINGS Details of construction and operation according to preferred embodiments of the invention, with respect to both the apparatus and method of the invention, will become readily apparent by reference to the following drawings wherein:

FIG. 1 is an elevational view of one embodiment of the invention, showing the same mounted within a manhole, which is shown in a cross section;

FIG. 2 is a side elevational view of the embodiment of the invention shown in FIG. 1;

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 1;

FIG. 4 is a partial internal view of the lower portion of FIG. 2 and drawn to an enlarged scale;

FIG. 5 is a top diagrammatic view, indicating use of the invention;

FIG. 6 is a partial, plan view of the central portion of FIG. 5, and drawn to an enlarged scale;

FIG. 7 is a view in perspective, showing the employment of the embodiment of the invention illustrated by FIGS. 1 through 6;

FIG. 8 is a view of one embodiment of a target which may be used with pipe sections as they are laid to indicate alignment of the pipe section with the energy beam;

FIG. 9 is a partial, side elevational view of the embodiment of the invention shown FIGS. 1 through 8, and illustrating one manner of adjusting the energy beam source about a vertical axis;

FIG. 10 is a plan view of the invention as illustrated in FIG.

FIG. 11 is a side, elevational view of another embodiment of the invention, with parts broken away to show interior detail;

FIG. 12 is a sectional view taken along lines 12-12 of H0. 1 1;

FIG. 13 is a view in perspective, similar to FIG. 7, but showing use of the second embodiment of the invention; FIG. 14 is a top plan view of a portion of the invention depicted in FIG. 11', and

FIG. 15 is a partial, plan view of the invention as illustrated in FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings by reference character, and in particular to FIGS. 1 through 8 thereof, the invention 10 is shown mounted within a manhole 12. While the invention has obvious utility in varied construction situations in the preferred embodiments of the invention, it will be shown being used to establish a reference line for the laying of sewer pipe. A transverse support 14 is provided, comprising a central rail segment 16, T-shaped in cross section; rail segment 16 includes cylindrical end pieces 18,18. A pair of common lolly jacks 20,20 are mounted on the free ends of cylindrical end pieces 18,18 and are used to firmly mount rail segment 16 within manhole 12. In other words, the entire support 14 comprises a common lolly column, well known in the construction trade, having a rail segment at its central portion.

An energy beam or light source 22, which in the preferred embodiment comprises a laser, is contained within a support tube 24, which is pendulously suspended from a pivot assembly 26. In this embodiment, pivot assembly 26 is best illustrated in FIGS. 3 and 6. Pivot assembly 26 comprises a support plate 28, beneath rail segment 16, a backing plate 30, a pair of adjustable clamps 32, 32 for retaining plates 28, 30 on rail segment 16, a generally U-shaped bracket 34, depending from backing plate 30, a pivot block 36 within bracket 34, and a pin 38 through the ears of bracket 34 and block 36. Each clamp assembly 32 includes a pair of spacers 40,40 a clamp plate 42, extending over the flanges of rail segment 16 and a threaded fastening screw 44, through clamp plate 42, and threaded to plates 28 and 30. Alternate loosening and tightening of screws 42 thereby permits linear adjustment of pivot assembly 26, and thus tube 24 and light source 22, along rail segment 16. A pair of balanced, coil springs 46, 46 may be inserted beneath backing plate 30, on pivot block 36 in order to stabilize the pivot block, and an incremental adjustment system 48 may be provided to incrementally rotate pivot block 36 about a vertical axis drawn through the center of pin 38. System 48 includes an ear 50 and an adjusting screw 52 threaded therethrough, and abutting the stem of rail segment 16.

Support tube 24 is connected to pivot block 36 by a pair of angled arms 54, 54 which may include hooks 56, 56 which comprise a storage rack for electrical line 58 of the light source 22 when the invention is not in use. As stated previously, in the preferred embodiment of the invention, energy beam source 22 comprises means for projecting a laser beam. As shown in FIG. 4, source 22 is mounted to pivot about a horizontal axis at its center of gravity by provision of an inner mounting ring 60 secured to source 22, an outer right 62, fitted tightly within tubular support 24, and a pair of pivot pins 64, 64 connecting rings 60,62; it is placed along the horizontal axis of rotation of the energy beam source 22. By this mode of construction, deviation of the source about the axis formed by pins 64,64 will not cause any pivotal movement of pivot block 36 about an axis through pin 38. If desired, a common spirit level 66 may be provided on the top of tubular housing 24 to visually check the stable, horizontal position of tube 24. A vertical adjustment system for source 22 denominated by numetal 68 is provided at the forward end thereof and comprises a lock collar 70 secured to laser 22, a threaded rod 72, pivotally connected to collar 70, and an adjustment knob 74, internally bored and threaded to rod 72. A compression spring 76 between the internal top wall of housing 24 and the top of collar 70, about rod 72 serves to stabilize laser 22 within housing 24. Additionally, a simple dial pointer and scale, attached to rod 72 and housing 24 may be provided to indicate deviation of laser 22 from a tube horizontal orientation (not shown). For protective purposes, housing 24 is normally capped at both ends and the front cap 78 (FIG. 1) may be slotted at 80 to allow passage of the beam therethrough. A pivoting-protective strip 82 serves to cover slot 80 when the invention is not in use.

An alternative construction of incremental adjustment system 48 is shown in FIGS. 9 and 10. In this embodiment,

plates 28 and 30 are replaced by a top plate 84, which is provided with curved slots 86, 88, and a backing plate pivotally secured to top plate 84 by pine 92. Ear 94, mounted on plate 84, has an internal bearing, (not shown) to receive an adjustment screw 96, which is in turn threaded to a pin 98, rotatably mounted in plate 90 about a vertical axis, pin 90 extending upwardly through slot 86. A capped pin 100, extending through slot 88, is secured to backing plate 90. Thus, rotation of adjustment screw 96 causes backing plate 90, block 36, arms 54, tubular housing 24 and a top 22 to rotate, incrementally, about a vertical axis formed by pin 92.

Turning now to FIGS. 5, 7 and 8 in particular, the operation and method of this embodiment of the invention will be explained. First, an offset line 102 is established at right angles, or 90 to the reference line 104 sought to be established, which in this case is coincident with the desired line and grade of the pipe to be laid This is illustrated in FIG. 7 wherein reference line 104 passes coaxially through a pipe segment 106. Offset line 102 is established by means of a transit and level (not shown) by any method common to the surveying art. Offset line 102 is physically represented by a pair of grade pegs 108,108, both set to a common, known grade. At this point in the method of the present invention, the further use of a transit and level becomes unnecessary. Then, support 14 is placed within manhole 12 and lolly jacks 20 are adjusted until support 14 is secured within the manhole. A spirit level (not shown) may be provided along rail 16 to indicate horizontal alignment of support 14. A chalkline (not shown) may be stretched from pegs 108.108 over manhole 12 to align rail 16 and offset line 102. At this point, clamp assemblies 32 may be employed to adjust housing 24 along rail 16 until it is placed the required known distance from one of the offset pegs 108. Before or after this operation, housing 24 may be vertically adjusted to the required depth beneath pegs 108,108 by intersecting the chalkline from pegs 108,108 across manhole 12 with a plumb bob and a tape measure (not shown). This may be done by loosening jacks 20 and physically moving rail 16 up or down or arms 54 may be of a common telescopic construction, to allow vertical movement of tube 24 with respect to pivot block 36 in which case rail 16 need not be moved. Telescopic support arms are common in the mechanical art and hence, are not indicated by the drawings. At this point, knob 74 on rod 72 may be threaded up or down until laser 22 projects a beam at the proper grade. Since tubular support 24 always remains on a horizontal plane, the setting of laser 22 to the desired grade may be accomplished elsewhere than on the job location, thereby dispensing with the need for any adjustment of the laser within its housing thereafter. In the event support tube 24 is not perfectly opposed 90 to rail 16, incremental adjustment system 48 may be employed to align tube 24 with another chalkline stretched across manhole 12 at 90 to offset line 102 (not shown). Obviously, a transit and/or a level might be used instead of chalklines, but the expense is generally unwarranted.

Although in the preferred embodiment, a light source comprising a laser is employed, any source which will project a narrow energy beam may be used in place of laser 22. The laser is preferred, because the spread" of a laser beam is only about 1 inch per l0,000 yards. Once the laser is set in place, it is ready for a pipe laying operation, indicated by the Trice and Blount et al. patents hereinbefore discussed. The method includes placing a target (FIGS. 7 and 8) over the end of each pipe segment 106. Target 110 includes an opaque or translucent face 112, having cross line indicia 114 thereon to indicate the center of the target. The target face 112 may include a series of concentric circles 116,116 and as a laser beam passes through the target, it will be interrupted by face 1 l2 and deviation of the pipe segment 106 from reference line 104 will be indicated thereon. Thus, pipe 106 may be moved until the reference line 104 represented by the laser beam, passes through the precise center of target 110. As each pipe segment is laid in place, it is similarly checked. It is readily apparent that as long as the reference line remains constant.

several miles of pipe may be laid from a single setting of the invention in place. Of greater importance is the fact that vibrations in the construction are a will have little effect on the invention, since housing 24 is pendulously suspended from a single pivot and any disruption of the invention will only cause housing 24 to seek a true horizontal plane, due to the balanced suspension of source or laser 22 within housing 24.

In the normal course of laying sewer pipe, a backhoe is employed (not shown) to dig a trench 118 for the sewer pipe 106. Again, any opaque or translucent surface may be placed in the trench as it is dug, so as to interrupt the laser beam along reference line 104 to keep the backhoe operation on a true course.

A more sophisticated embodiment of the invention is indicated by FIGS. 11 through 15. In this case, support 14 comprises a single, horizontal tube or column 120, having lolly jacks at each end thereof (not shown) functioning as explained in the description of the first embodiment above with respect to lolly jacks 20,20. Pivot assembly 26 includes a platform 122, a vertically movable, generally U-shaped pivot support block 124, a horizontal pivot pine 126 and a rockable platform 128 bored to receive pin 126 and includes a vertical screw 130, which receives laser support bracket 132, retained on the screw by suitable means, such as winged nut 134. Bracket 132 carries support tube 136, housing energy beam source 22; it is constructed similarly to support tube 24. Platform 122 is retained on tube 120 by means of a pair of clamping devices 138,138 and pivot support block 124 is vertically movable by means of a stationary worm 140, threaded through base member 142 of block 124. Worm 140 may be hand-adjusted by means of knob 144 secured thereupon. Numeral 146 denotes a transformer housing for energy beam source for laser 22.

Support tube 136 is retained on bracket 132 by an external collar 148 therearound. Laser 22 includes a ring 150, mounted about laser 22 at its center of gravity, which ring has an upper step portion 152 formed thereon for purposes to be described below. A pair of pivot pins, one of which is indicated in FIG. 11 by numeral 154, extend through collar 148 and tube 136, to ring 150, supporting laser 22 for tilting about a horizontal axis taken through the pins 154. In this embodiment, vertical adjustment system 68 for laser 22 within tube 136 includes a collar 156, having a screw 158 extending vertically upwardly through tube 136. An adjustment knob 160 internally bored and threaded to screw 158, is retained within limits by a pair of split ears 162 formed at the lower distal end of bracket 132. A refinement in this embodiment of the invention comprises horizontal deviation indicator means 164, best shown by FIGS. 11 and 12. Indicator 164 in and of itself is common in the mechanical arts, and its internal construction per se forms no part of the present invention. In its usual configuration, indicator 164 includes a dial 166 and a pointer 168 to indicate deviation of the laser 22 from true horizontal with respect to tube support 136. Normally, a dial 166 will be graduated in degrees or fractions of degrees. A plunger 170, depending from indicator 164 extends through tubular housing 136 to step 152 of laser ring 150. As laser 22 is rotated about a horizontal axis, formed by pins 154, plunger 170 will be raised or lowered and the resulting deviation will be indicated by pointer 168. A cover 171 may be provided to protect indicator 164 from dirt and debris. When the invention is in place, a spirit level 172 may be provided on housing 136 to indicate a true horizontal orientation.

The method of operation of this second embodiment of the invention is quite similar to the first embodiment described above.

For purposes of description, FIGS. 7 and 13 are comparable. Offsets 108,108 are adequately described hereinbefore. Support 14 is set in place as previously discussed. After this, the invention may be secured in place on support 14 by operation of clamps 138,138. For final adjusting of the invention in place, a T-bar 174 having indicator lines 176 and 178 may be employed. T-bar 174 may also include a pair of spirit levels 180,180. Laser 22 and housing 136 are established on the proper vertical offset by measuring the distance from the upper distal end of screw to T-bar means of a plum bob with a tape measure thereon 182. Final vertical adjustment may be accomplished by turning knob 144 to raise or lower laser 22 a slight distance. Alignment of beam 184 in a vertical plane may be accomplished by interrupting beam 184 with a prism 186 (FIG. 11) pivotally mounted by bracket 188 either to laser 22 or to the tubular housing 136 (not shown). The laser beam may be reflected along indicator line 178 on T-bar 174 until alignment is perfected. Incremental adjustment of tube 136 and laser 22 about a vertical axis formed by screw 130 is best executed by providing an adjustment screw 190 threaded through an ear 192 on platform 128 (FIG. 14). The proper grade for the sewer pipe to be laid may be established by rotating knob until the proper grade is indicated on horizontal deviation indicator means 164.

Obviously, both embodiments of the invention may include a pair of lasers (not shown) or energy beam sources 22 within the tubular housing. In this way, sewer pipe, for example, may be laid in either direction from a single setting of the invention. Additionally, T-bar 174 may be used for setting the first embodiment of the invention in place. In both embodiments, energy beam source 22 is pendulously suspended from a single horizontal pivot and the energy beam source 22 is perfectly balanced within its support housing, so that the housing itself always seeks a true horizontal orientation. Thus, the required grade to be indicated by the beam may be set in a workshop, or elsewhere, than on the job locatiomThereafter, the invention may merely be transported to the construction site and set in place without any further adjustment of laser or energy beam source 22 within its tubular support housing.

1. A system for projecting an energy beam as a reference line for construction purposes comprising:

a. a stationary support; and

b. an energy beam assembly, pendulously suspended about a horizontal axis from the support, and comprising: 1. a bracket, pivoted to the support; and 2. an energy beam source secured to the bracket, and balanced with respect to the pendulous suspension axis to seek a horizontal orientation 2. The system as recited in claim 1 wherein the energy beam source comprises means for projecting a narrow light beam.

3. The system as recited in claim 1 wherein the energy beam source comprises a laser.

4. The system as recited in claim 1 wherein the stationary support comprises;

a. a rigid, laterally extending support;

. b. a pivot block assembly, movable along the lateral support.

5. The system recited in claim 4 wherein the rigid, lateral support comprises a rail, inverted T-shaped in cross section, and the pivot block assembly comprises;

a. a support plate beneath the rail;

b. clamp means securing the support plate on the rail;

0. a U-shaped pivot mount depending from the support plate;

d. a pivot base, pivotally mounted in the U-shaped pivot mount, said bracket secured to said U-shaped mount; and

e. means for incrementally rotating said pivot base about a vertical axis.

6. The system as recited in claim 5 wherein said means for incrementally rotating said pivot base about a vertical axis comprise:

a. a vertical ear, mounted on the support plate; and

b. an adjustment screw, threaded through the ear and abutting said rail.

7. The system as recited in claim 5 wherein said means for incrementally rotating said pivot base about a vertical axis comprise:

a. a backing plate, pivotally mounted centrally beneath the support plate, for rotation in a horizontal plane, said pivot base being secured centrally thereon;

b. means defining a pair of curved slots in said support plate,

one on each side of the rail;

c. a first pin mounted on the backing plate and extending through one of the slots;

d. a second pin, mounted on the backing plate and extending through the other of said slots;

e. a vertical ear, mounted adjacent said one slot on the support plate; and

f. an adjustment screw, mounted for rotation in said ear and threaded through the first pin, said slots thereby defining the limits of rotation of the backing plate with respect to the support plate.

8. The system as recited in claim 4 wherein. the rigid, laterally extending support comprises a generally cylindrical column, and the pivot block assembly comprises:

a. a platform, mounted on the column;

b. adjustable clamp means securing the platform to the column;

c. a pivot base, to which the bracket is secured;

d. means for mounting the pivot base on the platform for rotation about a horizontal axis; and

e. means for incrementally, vertically moving the pivot base.

9. The system as recited in claim 8 wherein the pivot base includes means for incrementally rotating the bracket about a vertical axis, comprising;

a. a vertical shaft for receiving a free portion of the bracket;

b. means for rigidly securing the free portion of the bracket to the pivot base; and

c. an adjustment screw, mounted on the pivot base and operatively connected to the bracket for rotating the bracket about the vertical shaft.

10. The system as recited in claim 8 wherein the means for mounting the pivot base on the platform for rotation about a horizontal axis comprise:

a. a base member having two ears, said pivot base being received between the ears; and

b. a horizontally disposed pin, through the ears and the pivot base.

11. The system as recited in claim 10 wherein the means for incrementally, vertically moving the pivot base comprise:

a. means defining a threaded, vertical bore through the base member of the pivot base; and

b. a vertical worm, freely rotatably mounted with respect to the platform, and threaded through the vertical bore of the base member.

12. The system as recited in claim 1 wherein the energy beam source includes:

a. a housing, about the energy beam source, secured to the bracket;

b. means mounting the energy beam source for rotation about a horizontal axis, at its center of gravity; and

c. means for incrementally rocking the energy beam source about its horizontal axis mount, with respect to the housing.

[3. The system as recited in claim 12 wherein the means for incrementally rocking the energy beam source about its horizontal axis comprise:

a. a threaded, vertically disposed shaft, mounted on the impulse beam source and extending through the housing; and

b. a knob, internally bored and threaded to receive the vertical shaft, abutting the housing.

14. The system as recited in claim 13 wherein the means for incrementally rocking the energy beam source about its horizontal axis further include spring means mounted about the threaded, vertically disposed shaft, internally of the housing, for urging the energy beam source away from the knob.

15. The system as recited in claim 13 wherein the means for incrementally rocking the energy beam source about its horizontal axis further include means-indicating deviation of the energy beam source from the disposition of the housing, in

a vertical plane.

16. The system as recited in claim 12 wherein the energy beam source further includes a prism for interrupting and deflecting the impulse beam.

17. A method for establishing a light beam reference line for construction purposes comprising:

a. establishing a pair of reference points at a known elevation and along a line forming a predetermined angle with the intended reference line;

b. adjusting a light beam source, adjustably rotatable at its center of gravity about a horizontal axis within a housing which is pendulously suspended for free rotation in a vertical plane, within said housing in a vertical plane until the light beam coincides with the grade of the reference line;

c. placing the pendulously suspended housing light beam source approximately at the predetermined angle with respect to a line drawn through the reference points;

d. adjusting the light beam source housing vertically to coincide with the desired depth of the reference line by measuring, vertically, the distance between the reference points and the light beam source; and

e. pivoting the light beam source housing about a vertical axis until the beam is disposed at the predetermined angle to the line drawn through the reference points.

18. The method as recited in claim 17 wherein the step of pivoting the light beam source about a vertical axis further includes;

a. interrupting the light beam with a prism;

b. placing an opaque indicator above the prism-diverted beam, having a line thereon parallel with the reference line in a vertical plane; and

c. rotating the prism to display the beam along the indicator and rotating the housing until the beam coincides with the line on the indicator. 

1. A system for projecting an energy beam as a reference line for construction purposes comprising: a. a stationary support; and b. an energy beam assembly, pendulously suspended about a horizontal axis from the support, and comprising:
 1. a bracket, pivoted to the support; and
 2. an energy beam source secured to the bracket, and balanced with respect to the pendulous suspension axis to seek a horizontal orientation
 2. an energy beam source secured to the bracket, and balanced with respect to the pendulous suspension axis to seek a horizontal orientation
 2. The system as recited in claim 1 wherein the energy beam source comprises means for projecting a narrow light beam.
 3. The system as recited in claim 1 wherein the energy beam source comprises a laser.
 4. The system as recited in claim 1 wherein the stationary support comprises; a. a rigid, laterally extending support; b. a pivot block assembly, movable along the lateral support.
 5. The system recited in claim 4 wherein the rigid, lateral support comprises a rail, inverted T-shaped in cross section, and the pivot block assembly comprises; a. a support plate beneath the rail; b. clamp means securing the support plate on the rail; c. a U-shaped pivot mount depending from the support plate; d. a pivot base, pivotally mounted in the U-shaped pivot mount, said bracket secured to said U-shaped mount; and e. means for incrementally rotating said pivot base about a vertical axis.
 6. The system as recited in claim 5 wherein said means for incrementally rotating said pivot base about a vertical axis comprise: a. a vertical ear, mounted on the support plate; and b. an adjustment screw, threaded through the ear and abutting said rail.
 7. The system as recited in claim 5 wherein said means for incrementally rotating said pivot base about a vertical axis comprise: a. a backing plate, pivotally mounted centrally beneath the support plate, for rotation in a horizontal plane, said pivot base being secured centrally thereon; b. means defining a pair of curved slots in said support plate, one on each side of the rail; c. a first pin mounted on the backing plate and extending through one of the slots; d. a second pin, mounted on the backing plate and extending through the other of said slots; e. a vertical ear, mounted adjacent said one slot on the support plate; and f. an adjustment screw, mounted for rotation in said ear and threaded through the first pin, said slots thereby defining the limits of rotation of the backing plate with respect to the support plate.
 8. The system as recited in claim 4 wherein the rigid, laterally extending support comprises a generally cylindrical column, and the pivot block assembly comprises: a. a platform, mounted on the column; b. adjustable clamp means securing the platform to the column; c. a pivot base, to which the bracket is secured; d. means for mounting the pivot base on the platform for rotation about a horizontal axis; and e. means for incrementally, vertically moving the pivot base.
 9. The system as recited in claim 8 wherein the pivot base includes means for incrementally rotating the bracket about a vertical axis, comprising; a. a vertical shaft for receiving a free portion of the bracket; b. means for rigidly securing the free portion of the bracket to the pivot base; and c. an adjustment screw, mounted on the pivot base and operatively connected to the bracket for rotating the bracket about the vertical shaft.
 10. The system as recited in claim 8 wherein the means for mounting the pivot base on the platform for rotation about a horizontal axis comprise: a. a base member having two ears, Said pivot base being received between the ears; and b. a horizontally disposed pin, through the ears and the pivot base.
 11. The system as recited in claim 10 wherein the means for incrementally, vertically moving the pivot base comprise: a. means defining a threaded, vertical bore through the base member of the pivot base; and b. a vertical worm, freely rotatably mounted with respect to the platform, and threaded through the vertical bore of the base member.
 12. The system as recited in claim 1 wherein the energy beam source includes: a. a housing, about the energy beam source, secured to the bracket; b. means mounting the energy beam source for rotation about a horizontal axis, at its center of gravity; and c. means for incrementally rocking the energy beam source about its horizontal axis mount, with respect to the housing.
 13. The system as recited in claim 12 wherein the means for incrementally rocking the energy beam source about its horizontal axis comprise: a. a threaded, vertically disposed shaft, mounted on the impulse beam source and extending through the housing; and b. a knob, internally bored and threaded to receive the vertical shaft, abutting the housing.
 14. The system as recited in claim 13 wherein the means for incrementally rocking the energy beam source about its horizontal axis further include spring means mounted about the threaded, vertically disposed shaft, internally of the housing, for urging the energy beam source away from the knob.
 15. The system as recited in claim 13 wherein the means for incrementally rocking the energy beam source about its horizontal axis further include means-indicating deviation of the energy beam source from the disposition of the housing, in a vertical plane.
 16. The system as recited in claim 12 wherein the energy beam source further includes a prism for interrupting and deflecting the impulse beam.
 17. A method for establishing a light beam reference line for construction purposes comprising: a. establishing a pair of reference points at a known elevation and along a line forming a predetermined angle with the intended reference line; b. adjusting a light beam source, adjustably rotatable at its center of gravity about a horizontal axis within a housing which is pendulously suspended for free rotation in a vertical plane, within said housing in a vertical plane until the light beam coincides with the grade of the reference line; c. placing the pendulously suspended housing light beam source approximately at the predetermined angle with respect to a line drawn through the reference points; d. adjusting the light beam source housing vertically to coincide with the desired depth of the reference line by measuring, vertically, the distance between the reference points and the light beam source; and e. pivoting the light beam source housing about a vertical axis until the beam is disposed at the predetermined angle to the line drawn through the reference points.
 18. The method as recited in claim 17 wherein the step of pivoting the light beam source about a vertical axis further includes; a. interrupting the light beam with a prism; b. placing an opaque indicator above the prism-diverted beam, having a line thereon parallel with the reference line in a vertical plane; and c. rotating the prism to display the beam along the indicator and rotating the housing until the beam coincides with the line on the indicator. 